Israeli helicopter gun ships attacked Palestinian police headquarters in Gaza City. The rockets scored a direct hit on the building, smashing walls and shattering windows. A number of explosions were heard and smoke rose from the headquarters as people ran frantically into the street.

The Israeli army says the facility was being used to produce weapons, including mortar bombs. Palestinians have frequently fired mortars at Jewish settlements in the Gaza Strip.

The police compound is close to the offices of Palestinian President Yasser Arafat, although he was not in the area at the time of the attack.

The raid followed the deaths of six Palestinians killed in a powerful explosion near the West Bank town of Jenin. The explosion blew the roof off a shack being used to store car parts near the Farah refugee camp.

Palestinian security officials say some of the men were on Israel's most-wanted list for planning attacks against Israelis. The officials said the Israeli army fired at the building, calling it a targeted assassination. Palestinian Cabinet Secretary Ahmed Abdel Rahman said Israel's policy of assassinations will "destroy any hope for peace". He pledged that "resistance will continue". Palestinians accuse the Israeli army of assassinating about 40 activists in recent months.

Israeli officials denied involvement, suggesting a bomb the men may have been building went off prematurely. Raanan Gissen is a spokesman for Israeli Prime Minister Ariel Sharon. "Well, I can tell you for certain that this particular incident had nothing to do with Israeli security forces," he said. "As I said, occupational hazard, you play with explosives, you get burned." Mr. Gissen says three of the men killed in the explosion were members of the Palestinian military intelligence force.

More than 670 people, mostly Palestinians, have been killed since the conflict began last September.